Typescript (photocopy). / Digitized by Kansas Correctional Industries / K-State Libraries' copy missing leaf 1 of introduction.

Time-delay dynamical systems are used to model many real-world engineering systems, where the future evolution of a system depends not only on current states but also on the history of states. For this reason, the study of stability and control of time-delay systems is of theoretical and practical importance. In this thesis, we develop several stability analysis frameworks for dynamical systems in the presence of communication and computation time-delays, and apply our results to different challenging engineering problems. The thesis first considers delay-independent stability of positive monotone systems. We show that the asymptotic stability of positive monotone systems whose vector fields are homogeneous is independent of the magnitude and variation of time-varying delays. We present explicit expressions that allow us to give explicit estimates of the decay rate for various classes of time-varying delays. For positive linear systems, we demonstrate that the best decay rate that our results guarantee can be found via convex optimization. We also derive a set of necessary and sufficient conditions for asymptotic stability of general positive monotone (not necessarily homogeneous) systems with time-delays. As an application of our theoretical results, we discuss delay-independent stability of continuous-time power control algorithms in wireless networks. The thesis continues by studying the convergence of asynchronous fixed-point iterations involving maximum norm pseudo-contractions. We present a powerful approach for characterizing the rate of convergence of totally asynchronous iterations, where both the update intervals and communication delays may grow unbounded. When specialized to partially asynchronous iterations (where the update intervals and communication delays have a fixed upper bound), or to particular classes of unbounded delays and update intervals, our approach allows to quantify how the degree of asynchronism affects the convergence rate. In addition, we use our results to analyze the impact of asynchrony on the convergence rate of discrete-time power control algorithms in wireless networks. The thesis finally proposes an asynchronous parallel algorithm that exploits multiple processors to solve regularized stochastic optimization problems with smooth loss functions. The algorithm allows the processors to work at different rates, perform computations independently of each other, and update global decision variables using out-of-date gradients. We characterize the iteration complexity and the convergence rate of the proposed algorithm, and show that these compare favourably with the state of the art. Furthermore, we demonstrate that the impact of asynchrony on the convergence rate of the algorithm is asymptotically negligible, and a near-linear speedup in the number of processors can be expected. / Tidsfördröjningar uppstår ofta i tekniska system: det tar tid för två ämnen attblandas, det tar tid för en vätska att rinna från ett kärl till ett annat, och det tar tid att överföra information mellan delsystem. Dessa tidsfördröjningar lederofta till försämrad systemprestanda och ibland även till instabilitet. Det är därförviktigt att utveckla teori och ingenjörsmetodik som gör det möjligt att bedöma hur tidsfördröjningar påverkar dynamiska system. I den här avhandlingen presenteras flera bidrag till detta forskningsområde. Fokusligger på att karaktärisera hur tidsfördröjningar påverkar konvergenshastigheten hos olinjära dynamiska system. I kapitel 3 och 4 behandlar vi olinjära system varstillstånd alltid är positiva. Vi visar att stabiliteten av dessa positiva system är oberoende av tidsfördröjningar och karaktäriserar hur konvergenshastigheten hos olinjära positiva system beror på tidsfördröjningarnas storlek. I kapitel 5 betraktar vi iterationer som är kontraktionsavbildningar, och analyserar hur deras konvergens påverkas av begränsade och obegränsade tidsfördröjningar. I avhandlingens sistakapitel föreslår vi en asynkron algoritm för stokastisk optimering vars asymptotiska konvergenshastighet är oberoende av tidsfördröjningar i beräkningar och i kommunikation mellan beräkningselement. / <p>QC 20151204</p>

published_or_final_version / Electrical Engineering / Master / Master of Science in Engineering

No description available.

No description available.

Widespread use of childhood vaccination has significantly reduced the burden of childhood disease, however a subset of parents are choosing to delay or refuse available vaccines. This study analyzed data collected from a large surveillance study to examine the parents’ attitudes about vaccines and the prevalence of vaccine hesitancy (vaccine delay and refusal) in an urban clinic population. The parents of 961 children attending the Boston Medical Center Pediatrics department participated in the study. Parental responses to four vaccine questions were used to assess vaccine attitudes. Log-Binomial Regression models were used to evaluate the relationship between comorbidity status and birth order with vaccine delay or refusal. In this study population, parents reported generally positive attitudes toward vaccination. The majority (87%) believed that vaccines were necessary to protect their child. Approximately 16% of parents reported that had delayed or refused a vaccine and 24% of parents indicated that they did not believe or were unsure if other parents vaccinating their children. When asked the reason for their choice, parents who only delayed frequently cited logistic concerns like a missed appointment, whereas parents who refused more often cited personal beliefs, such as concerns that their child could become ill from vaccination. Finally, parents of children with a comorbidity were more likely to refuse a vaccine than parents of children without comorbidity (Adjusted RR=1.8, 95% CI: 1.1, 2.9). While parents were generally positive toward vaccines, for the small portion of parents refusing vaccines, further work could help to better explain their motivations.

The purpose of the current study is to apply the delay and probability discounting in the areas of parent training and probability of success of treatment. There was a total of 31 participants that completed one demographic questionnaire and two probability and delay discounting surveys either via computer or with paper and pencil. Participants had two options in the surveys: one was an immediate reward, and one with a probability delay. The first survey gave scenarios of hours of parent training, the second was a monetary probability discounting survey.

Functional differential equations with delay have long been studied due to their practical applications. For the delay term is not a constant number, many researches study the case when this deviating argument depends on the state variable. So we deal with the differential and functional equations involving with the compositions of the unknown function, i.e. the iterative functional differential equations (IFDEs) and iterative functional equations (IFEs) without derivative. The main purpose of this dissertation is to investigate the solutions of such equations, including their analytic solutions, numerical solutions and qualitative behaviors. First, we survey some well known differential equations of this type which possess analytic solutions. Then the classical method of undetermined coefficients is used to compute these power series solutions for the first order IFDEs in Chapter 1, the second order IFDEs in Chapter 2 and FDEs in Chapter 3. Taylor series method is also used to get these analytic solutions in Chapter 4. Systematical method is found to locate the fixed point in generalized sense, so we can use these methods to calculate the coefficients of their analytic solutions. Furthermore, we also establish the existence and uniqueness theorem for analytic solution in Chapter 5. Second, we survey the known existence and uniqueness theorems of solutions for these IFDEs and FDEs in Chapter 6. Then we apply Schauder fixed point theorem to establish new existence theorems of local solutions for general IFDEs. Under certain conditions, these local solutions can be extended to global solutions. Chapter 7 deals with the simplest IFDEs the Eder's equation. We extend the qualitative properties of this case and find its solution is not unique. In Chapter 8, we use Euler method to get the numerical solution of IFDEs. Under some conditions, we have the error analysis on these equations. In Chapter 9, we employ the method of undetermined coefficients, Taylor series, Picard's iteration and Si's methods to get their analytic solutions. Their comparisons, the advantage and disadvantage of these methods are also discussed.

This thesis concerns delay-dependent robust stability analysis and stabilization for time-delay system with uncertainties. By choosing new Lyapunov-Krasovskii functional and using methods which can reduce conservativeness of stability condition in the literature, new delay-dependent sufficient stability conditions are obtained in terms of linear matrix inequality. It is shown that the new stability conditions can provide less conservative results than some existing ones. Furthermore, the new stability conditions are also used to design the state feedback controllers. Finally, numerical examples are given to show the derived results and compared with results in the literature.

The operating clock frequency is determined by the longest signal propagation delay, setup/hold time, and timing margin. These are becoming less predictable with the increasing design complexity and process miniaturization. The difficult challenge is then to ensure that a device operating at its clock frequency is error-free with quantifiable assurance. Effort at device-level engineering will not suffice for these circuits exhibiting wide process variation and heightened sensitivities to operating condition stress. Logic-level redress of this issue is a necessity and we propose a design-level remedy for this timing-uncertainty problem. The aim of the design and analysis approaches presented in this dissertation is to provide framework, SABRE, wherein an increased operating clock frequency can be achieved. The approach is a combination of analytical modeling, experimental analy- sis, hardware /time-redundancy design, exception handling and recovery techniques. Our proposed design replicates only a necessary part of the original circuit to avoid high hardware overhead as in triple-modular-redundancy (TMR). The timing-critical combinational circuit is path-wise partitioned into two sections. The combinational circuits associated with long paths are laid out without any intrusion except for the fan-out connections from the first section of the circuit to a replicated second section of the combinational circuit. Thus only the second section of the circuit is replicated. The signals fanning out from the first section are latches, and thus are far shorter than the paths spanning the entire combinational circuit. The replicated circuit is timed at a subsequent clock cycle to ascertain relaxed timing paths. This insures that the likelihood of mistiming due to stress or process variation is eliminated. During the subsequent clock cycle, the outcome of the two logically identical, yet time-interleaved, circuit outputs are compared to detect faults. When a fault is detected, the retry sig- nal is triggered and the dynamic frequency-step-down takes place before a pipe flush, and retry is issued. The significant timing overhead associated with the retry is offset by the rarity of the timing violation events. Simulation results on ISCAS Benchmark circuits show that 10% of clock frequency gain is possible with 10 to 20 % of hardware overhead of replicated timing-critical circuit.